Your question Hello, after setting up things for gmail, this works now. but outlook still gives an error: lookup error: DNS resolution error: DNS error: DNSSEC validation failed what should I do to solve this?

It’s due to a hickory-resolver bug, rollback to the previous version or wait a few days until 0.16.22.

Let me look at the resolver page fully to see variants (system, cloudflare, custom, etc.) and DNSSEC-related notes. A “DNSSEC validation failed” lookup error usually surfaces from the DANE/TLSA lookup step, and it means the resolver Stalwart is using got a cryptographically invalid (bogus) DNSSEC r…

yes, i’m on version 0.16.21 too.

Same symptom here on 0.16.21. In my case the resolver choice made no difference and dane set to disable did not help either, the validation runs regardless of that setting. thornbux bisected it in the linked thread: 0.16.20 is fine, 0.16.21 is not, the change is in hickory-resolver 0.26.1 to 0.2…

Same problem here, had to go back to 16.20.

Happening to me too, since the 16.21 update. Proton domains are also affected.

Version 0.16.22 did not fix the issue. I am having the exact same issue with Proton domains at the very least.

Also continuing to see this error with 0.16.22; with proton domains and gmail.

[image] Outbound delivery to all .org and .io recipients stalls with "DNSSEC validation failed" beetleIssues This is hickory bug, added a workaround to limit concurrency to 1 in v0.16.23 (yet to be released). Further Hickory issue resolved in v0.16.23

I confirm the issue seems to be resolved in v0.16.23 :slightly_smiling_face:

Transmission problem to outlook.com

Questions

thornbux September 10, 2026, 10:52am 3

This problem could be related to MX lookup fails with "DNSSEC validation failed" for signed zone (mail.de, RSA/SHA-512) on 0.16.21, regardless of DANE setting if you are on version 0.16.21

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Transmission problem to outlook.com

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